The other day I received and email about a broken intercom system at Southwest Elementary.  I was curious about this system because in the email was a picture of the system which made it appear to be an old early pentium or perhaps 486 based PC.

As you can see from the photo the device is clearly in a PC chasis but is it a PC?

On site taking a closer look it appears that the system is somewhat of a hybrid.  It uses a standard PC power supply although BIOS is customized to run through on board modules and the program is run by ROM chips attached to a circuit board powered by a molex connector instead of a traditional hard drive.  Probably a good idea that this machine does not use a hard drive since with being powered on almost 24/7 this part would have failed much earlier.

Inside the machine are a series of peripheral expansion cards ISA slots – a quick look at the board confirms this machine to be running an386 or i486 with ISA expansion ports.  (I remember my first soundblaster card used the 8 bit ISA slot and my second computer 486 used the ISA 16 with a Soundblaster Pro 16.

On the site I could here a Pop sound from the power supply when it was attempted to power-on, on closer inspection I could see a blown capacitator inside.  Considering the machine has been running for years not stop without a break I am not surprised this old 250 watt power supply finally died.

Luckily I store lots and lots of parts at the High School and simply swapped out this part with a newer 350 Watt P4 power supply (obviously not using the P4 extension) and connected it to the motherboard and to one circuit board via a molex connector – and wha laaa the machine came to life and is working.

This is a picture of the old power supply – standard ATX 250 watt power supply.

Replaced it with a ATX 20 pin + 4 pin 350 watt supply (leaving the extra 4 pin not attached)

Here is shot of the back where the custom extension ISA peripherals attach at the back.  Not really much of a point to this entry other than I still find myself fascinated by the endless combination of PC components used in any number of devices.  Since my first computer was a 286 12 mhz machine with 512 kb of ram (yes half of 1 mb) I like it when I encounter legacy hardware that still works great.